When using potentiometers for rotary toggle controls, e.g., for activating or de-activating and adjusting the temperature of a hotplate of a hob or oven, generally there is no additional master switch for activating or deactivating the hotplate or oven. Deactivation of the hotplate or oven should, however, still be reliably possible in the case of a fault or a defect to the potentiometer or control device. Various different solutions are known for this.
In one such solution, the potentiometer can be constructed as a double potentiometer, where a second, redundant potentiometer is provided. However, such double potentiometers are comparatively expensive. Moreover an output voltage of the additional potentiometer must be evaluated, so that there is a need for a further associated, analog measurement terminal within the control device.
A further possibility is provided by the use of an additional power switch or power contact, which is in operative connection with the rotary toggle and, independently of the toggle position determined by the potentiometer, interrupts a supply voltage of an associated heater element in an off position of the rotary toggle. Apart from the costs caused by the additional power switch, there is an increased cabling expenditure on the mains voltage side, so that the manufacturing costs also rise.
On using so-called code switches, e.g., with a Gray code, for determining the rotary toggle position, an off position can be detected by an additional slider path specifically provided for this purpose. However, the additional slider path increases the manufacturing costs. Furthermore, for evaluating the slider path position, there must be a further associated evaluation terminal within the control device.
Therefore, there is a need for the provision of a method for evaluating a potentiometer, as well as a circuit arrangement having a potentiometer of the aforementioned type, which permits a reliable evaluation of a conventional potentiometer with respect to its functionality and the potentiometer position and which can be inexpensively implemented with limited space demands.